Pd Atomic Chain Formation as a Result of Submonolayer Deposition of $3d$ Metals on Pd(110)

Submonolayer deposition of $3d$ transition metals such as Cr, Mn, Fe, Co, and Ni on Pd(110) at room temperature causes the formation of monoatomic chains of Pd as identified with scanning tunneling microscopy and spectroscopy. In agreement with recent theoretical predictions [Phys. Rev. B 79, 155410 (2009)], the substitution of Pd substrate atoms with the deposited atoms of $3d$ metals is found to be responsible for the formation of Pd atomic chains. This finding clarifies the long-debated issue about the chemical composition of the atomic chains grown on Pd(110) and points out the intriguing processes in the formation of self-assembled and self-organized nanostructures.

Figure 1

Topography (a), (b), and $dI/dU$ spectra (c) of atomic wires formed by Fe and Co deposition on Pd(110) at RT. STM image conditions: $50\mathrm{nm}\times 50\mathrm{nm}$; $V=0.4\mathrm{V}$, $I=20\mathrm{nA}$. The spectrum of Pd substrate is plotted for comparison.

Figure 2

Topography image of Fe adatoms deposited at 6 K. Imaging conditions: $15\times 9.1\mathrm{nm}$; $V=24.9\mathrm{mV}$, $I=20\mathrm{nA}$. (b) $dI/dU$ spectra for Fe monomers, dimers, and trimers [marked by stars in (a)] on Pd(110) taken at the deposition temperature (6 K). The spectra of Fe adatoms show shoulders or peaklike features at around 0.3–0.5 V.

Figure 3

(a) Topography image for 0.12 ML Fe deposited on Pd(110) at $T=40\mathrm{K}$ and then slightly warmed up to RT. Imaging conditions: $6\times 3.3\mathrm{nm}$; $V=17.6\mathrm{mV}$, $I=17.7\mathrm{nA}$. (b) The $dI/dU$ spectra of an atomic chain taken at the positions marked by white spots in (a). Most of the spectra (drawn in black) are identical to the spectra of Pd. Only the spectra drawn in red, recorded at two positions [marked by white arrows in (a)], show a peak (indicated by red arrows) at around 0.47 and 0.52 V, which confirm the presence of Fe atoms at these positions.